Shortawn Foxtail (Alopecurus aequalis) is a monocot weed in the Poaceae family. In Japan this weed first evolved multiple resistance (to 2 herbicide sites of action) in 2004 and infests Spring Barley, and Wheat. Multiple resistance has evolved to herbicides in the Groups B/2, and K1/3. These particular biotypes are known to have resistance to thifensulfuron-methyl, and trifluralin and they may be cross-resistant to other herbicides in the Groups B/2, and K1/3.

The 'Group' letters/numbers that you see throughout this web site refer to the classification of herbicides by their site of action. To see a full list of herbicides and HRAC herbicide classifications click here.

Field, and Laboratory trials comparing a known susceptible Shortawn Foxtail biotype with this Shortawn Foxtail biotype have been used to confirm resistance. For further information on the tests conducted please contact the local weed scientists that provided this information.

Genetics

Genetic studies on Group B, K1/2, 3 resistant Shortawn Foxtail indicate that the inheritance is determined by a one gene trait. There may be a note below or an article discussing the genetics of this biotype in the Fact Sheets and Other Literature

Mechanism of Resistance

Studies on the mechanism of resistance of multiple resistant Shortawn Foxtail from Japan indicate that resistance is due to an altered target site. There may be a note below or an article discussing the mechanism of resistance in the Fact Sheets and Other Literature

Relative Fitness

There is no record of differences in fitness or competitiveness of these resistant biotypes when compared to that of normal susceptible biotypes. If you have any information pertaining to the fitness of multiple resistant Shortawn Foxtail from Japan please update the database.

The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Japan have been instrumental in providing you this information. Particular thanks is given to Saima Hashim for providing detailed information.

BACKGROUND: Trifluralin-resistant biotypes of water foxtail (Alopecurus aequalis) have been identified in wheat fields from northern Kyushu, Japan. Water foxtail is a winter-annual grassy weed, causing substantial crop losses. This study reports on mutation in α-tubulin (TUA) genes from water foxtail, the site of action of trifluralin. RESULTS: Two trifluralin-sensitive (S) Chikugo and Ukiha biotypes and four trifluralin-resistant (R) Asakura-1, Asakura-2, Tamana and Tosu biotypes of water foxtail were used for herbicide resistance analysis. R biotypes showed 5.7-30.7-fold trifluralin resistance compared with the S biotypes. No differences in the uptake and translocation of 14C-trifluralin were observed between Chikugo (S) biotype and Asakura-1 (R) biotype. Most of the 14C detected in the plant material was in the root tissue, and no substantial increases were noted in shoot tissues. Comparative TUA sequence analysis revealed two independent single amino acid changes: change of Val into Phe at position 202 in TUA1 and change of Leu into Met at position 125 in TUA3 in Asakura-1 biotype. In the Tamana (R) biotype, two amino acid changes of Leu to Phe at position 136 and Val to Phe at position 202 were observed in the predicted amino acid sequence of TUA1, compared with Chikugo (S) biotype. CONCLUSION: The results provide preliminary molecular explanation for the resistance of water foxtail to trifluralin, a phenomenon that has arisen as a result of repeated exposure to this class of herbicide. This is the first report of α-tubulin mutation in water foxtail and for any Alopecurus species reported in the literature..

Alopecurus aequalis, a predominant weed species in wheat and oilseed rape fields, can no longer be controlled by mesosulfuron-methyl application after continuous use over several years. Based on dose–response studies, the putative resistant populations, JTJY-1 and JHHZ-1, were found to be resistant to mesosulfuron-methyl, with resistance index values of 5.5 and 14, respectively. Sensitivity assays of the mesosulfuron-methyl-resistant populations to other herbicides revealed that the JTJY-1 population had moderate or high cross resistance to sulfonylureas (SUs) and triazolopyrimidines (TPs), but displayed a low level resistance to imidazolinones (IMIs). JTJY-1 also had high multi-resistance to ACCase inhibitors, but remained susceptible to photosystem II inhibitors. The JHHZ-1 population was resistant to all ALS inhibitors tested, but was sensitive to ACCase inhibitors and photosystem II inhibitors. To clarify the molecular basis of resistance in JTJY-1 and JHHZ-1 population, the ALS and ACCase gene were sequenced. Two ALS mutations (Pro-197-Thr or Trp-574-Leu) were detected in the mesosulfuron-methyl-resistant plants. The ACCase gene analysis revealed that the resistant JTJY-1 population had an Ile-1781-Leu mutation. Furthermore, the presence of two different target site resistance (TSR) mechanisms (ALS and ACCase mutations) existing simultaneously in individual A. aequalis was firstly documented in the presented study..

Herbicide resistance or tolerance in weeds mediated by cytochrome P450 monooxygenase is a considerable problem. However, cytochrome P450 mediated resistance or tolerance in weeds was less studied. Thus, in this work, the role of the cytochrome P450 monooxygenase in the different responses of Poa annua and Alopecurus aequalis to fenoxaprop-P-ethyl was studied. We found that the effect of fenoxaprop-P-ethyl could be synergized by piperonyl butoxide (PBO) in P. annua, but not by malathion. After being treated with fenoxaprop-P-ethyl (containing mefenpyr-diethyl), the contents of cytochrome P450 and cytochrome b5 in P. annua increased significantly compared to plants treated with mefenpyr-diethyl only or untreated plants. However, the increase was less in A. aequalis, which was susceptible to fenoxaprop-P-ethyl. The activities of ρ-nitroanisole O-demethylase (PNOD), ethoxyresorufin O-deethylase (EROD), ethoxycoumarin oxidase (ECOD) and NADPH-dependent cytochrome P450 reductase mediated by cytochrome P450 monooxygenase increased in P. annua after treatment with fenoxaprop-P-ethyl, especially the activities of ECOD and cytochrome P450 reductase. Besides this, cytochrome P450 monooxygenase activity toward fenoxaprop-P-ethyl in P. annua increased significantly compared to untreated or treated with mefenpyr-diethyl plants and treated or untreated A. aequalis. Cytochrome P450 monooxygenase may play an important role in the different responses to fenoxaprop-P-ethyl in P. annua and A. aequalis..

Uchikawa, O. ; Miyazaki, M. ; Tanaka, K.. 2007.
Occurrence of resistant biotype water foxtail (Alopecurus aequalis) to some herbicides in wheat fields in Fukuoka prefecture, and the control method of its biotype.
Journal of Weed Science and Technology52
:
125 - 129.

In wheat paddy fields in Fukuoka prefecture which used thifensulfuron-methyl, a herbicide continuously in seven year, water foxtail (A. aequalis) in which the herbicidal activity was inferior arose As the results, the sensitivity test of the herbicide variously using both biotype seeds, and it was confirmed that the susceptibility lowered for thifensulfuronmethyl and dinitroaniline herbicide. As simple method test of herbicide resistant water foxtail, it was clarified that to use rooting method for sulfonylurea herbicide resistant weeds in summer paddy weeds were possible of this species. The fields which occurred the resistant biotype, it was clarified that the pendimethalin, thiobencarb and linuron mixture is effective..